In comments on this post, Tim and Ohioan both noted that the massive numbers of fruit flies breeding were enough to lead to macro-evolutionary changes over time. Even if the odds were billions-to-one against advantageous structural changes in genetic material, the fact that there are so many fruit flies producing so many offspring makes it conceivable.
Hooray for fruit flies!
How about elephants?
There aren't many of them and elephant cows produce a single calf every 5 years or so. Wouldn't evolution grind to a halt as the higher-order species produced so few offspring? If you need a billion hatchlings / calves / lambs to get a single new species with a new genetic structure instead of modification to existing genes, wouldn't it take practically forever to make those changes?
I've got a counter-argument to this line of thought, but I'm interested in what others have to say.
Aside: The original posts weren't really designed to question evolution, but were about Darwinian dogma being essentially religious. Still, it's a fun discussion and everyone's been quite pleasant, so let's see where else it goes.
18 comments:
Well I can't say for sure, but figures of merit seem like...
First if an elephant embryo has a negative mutation most of the time it wouldn't be carried to term so the time to the next embryo would probably be like 1 year not 5. Second let's guess that an elephant need to be like 10 to reach breeding age then has calves spaced about every 5 years (I won't look up these numbers, the worst guess is yet to come and will dominate the arguement's uncertainty). That gives us an average generation of like 20 years.
Now let's ask: if we had two distinct breeding groups of elephants (say one is in Africa and the other in Asia - like the two species I know about) how many mutations would it take to make them separate species? I really don't know. For fun let's say a million. How many mutations occur in a generation (or is it generations per mutation - I really don't know). Here's another WAG, let's call it one. One base pair change per generation.
So how long to get a million changes? About 20 million years. Well really more like 10 million years since both populations will be changing.
This number is close enough for me to believe it represents a crude approximation to reality.
OK, I anticipated this response. If it only takes 1,000,000 offspring to get a substantive mutation, then we should have seen this in fruit flies several times over by now.
We've got a lot of added fun because we don't know for sure what DNA does.
We know what some parts do-- at least, we're pretty dang sure-- but that's a tiny chunk.
Depending on how you define mutations, every generation has them; if I remember right, there's some swapping in the strands before the gamite even heads out. (Or maybe it's when they join? My memory is fuzzy, and I don't want to fight with my dang bookmark collection right now.)
We've got lots of examples of stuff breaking-- extra wings on fruit flies (both with and without repeated segments, iirc), albinos, red angus*-- but where's the stuff that's new and works?
*******
You might have fun over on this post:
https://madgeniusclub.com/2016/10/22/the-squishy-sciences/
*yes, really-- they're a pretty common mutation that will pop up in black angus herds. I seem to remember they're more common, the purer your stock-- so if you use cows that are hybrids, say selecting for hereford crosses in your replacement cows, you can have a higher chance of all black calves than if you stick with pure certified black angus cows. It matters to some buyers, don't ask me why. :D
Regarding the fruit flies, it looks like we *have* seen speciation in the lab (and we'd see it more if laboratories were actually trying to do it[1], instead of the standard procedure being to buy their fruit fly stocks from centralized suppliers, run their genetics experiments, and then dispose of their fruit flies when finished because maintaining a culture is a hassle and they can always buy more when they want them). Here are a couple of papers that I found with a few minutes poking around, I'm sure there are more.
Sympatric Host Race Formation and Speciation in Frugivorous Flies of the Genus Rhagoletis (Diptera, Tephritidae), Guy L. Bush, Evolution, Vol. 23, No. 2 (Jun., 1969), pp. 237-251http://www.jstor.org/stable/2406788?seq=1#page_scan_tab_contents
Dobzhansky, Th., and O. Pavlovsky, 1971. "An experimentally created incipient species of Drosophila", Nature 23:289-292.
As for the difference in evolution rate between large mammals like elephants, and small animals like insects, yes, this is a fact. Insects really do evolve about an order of magnitude more rapidly than mammals. The most obvious evidence of this is on my bookshelves right now: my copy of "Mammals of North America" is a comprehensive list of every known mammal species found in the continental US, and it lists maybe 450 species. Meanwhile my copy of "Owlet Caterpillars of Eastern North America", which is only dealing with a *single family* of moths, is this monstrous tome including over 2200 species, and the authors note that it is still incomplete. The insects are clearly speciating much, much faster.
And on elephants specifically, I think we need to be careful not to be fooled by size into thinking that their differences from other mammals are so vast. Increasing or decreasing size by breeding is easy. Just look at wolfhounds vs. chihuahuas, or those tiny toy horses vs. Clydesdales, both of which were mostly accomplished in less than about 2000 years, which comes to only a few hundred generations. And elongating a snout isn't really that big of an alteration, compared to sprouting a new limb altogether, or completely switching from herbivore to carnivore, or becoming able to eat plants that are aggressively toxic to everything else, or developing new and exotic chemicals to spray on attackers, or going from being 99% killed by a new pesticide to not being noticeably affected by it at all, all of which are things that the much faster-breeding insects have accomplished.
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[1] There are certain classes of experiments that are really hard to get funding for. One of them is long-term breeding experiments, because you need to run them for years and years (and since it depends on random availability of traits, there is no guarantee of success), while all of the funding sources that I'm aware of (both government and private) get really reluctant to support anything for more than 3 years at a time, and hardly ever more than 5 years. Breeding separate fruit fly populations over a few decades to observe speciation would be a really hard sell, so I'm not too surprised that there aren't scads and scads of researchers doing it, even though I expect that a lot would like to.
It's not a new species, but it's interesting:
https://en.m.wikipedia.org/wiki/Russian_Domesticated_Red_Fox
It's been going on almost 60 but it's in financial straights.
"In comments on this post, Tim and Ohioan both noted that the massive numbers of fruit flies breeding were enough to lead to macro-evolutionary changes over time."
No, they asserted, they did not "note". Had they noted, then there would be some actual evidence that "the massive numbers of fruit flies breeding [are] enough to lead to macro-evolutionary changes over time", in the for of actual "macro-evolutionary changes", to which they could point.
"... how many mutations would it take to make them separate species?"
Speciation is, and always has been, a red-herring.
The difference between a mouse(-like creature) and a bat is not mere speciation. The difference between a bat that uses echo-location and one that does not is not mere speciation.
It's all the rage these days to say that say that modern humans have a statistically significant amount of Neanderthal DNA in our collective genome (*). So, Hell! the difference between Homo sapiens sapiens and Homo sapiens neanderthalensis isn't even speciation.
(*) And I have no reason to doubt that that is true, But then, I never did believe that Neanderthals were a different species.
Tim, did the new flies have more than 8 chromosomes? I get that they have stable and significantly different characteristics, but I wonder about genetic structure differences.
As for elephants and flies, my point here was that the species is irrelevant. If I understand the argument, what you need is enough offspring and you'll get mutations leading to new genetic structures. Well, if all you need is a couple million, then humans would have seen it by now as well as fruit flies. If you need more than that, then creatures like elephants might never see it at all. I don't see what the size or shape of the critter matters, it's all about statistics.
By the way, Tim, you got at least part of my counter-argument. The quantity of species in the insect world vs. that of the mammals is an indicator of at least partial evolutionary success here.
K T Cat: "Still, it's a fun discussion and everyone's been quite pleasant ..."
You have an interesting understanding of "quite pleasant". Observe --
Tim Eisele: "[to paraphrase: you cannot make scientific predictions about how 'evolution' will procede.]"
Ilíon: "^ What you're saying is that 'evolution' isn't a science."
Tim Eisele: "Ilion, that makes even less sense than your usual non-sequitors."
*THAT* is how Darwinists "reason" and "argue".
"That should have been a yellow card and a penalty kick, but the referee has waved 'play on!'"
;-)
Going back to the statistics, forget about the experiments, look at nature and consider the number of fruit fly babies on the planet to the number of elephants. If elephants could evolve over 10,000,000 years, then fruit flies ought to be doing it every, what, 5 years?
How about sponges? Lobsters? Minnows?
KT: regarding the chromosome numbers, I agree that it is not entirely clear how the changes in chromosome numbers happen. It raises obvious who-do-I-mate-with-now? issues, and it is clearly fantastically rare, otherwise we'd see it happening before our eyes all the time. But I'd also like to note that while a change in chromosome number would be sufficient to make a new species, it clearly isn't necessary: just as one example, gorillas, chimpanzees, and orangutangs all have 48 chromosomes, but are quite different from each other otherwise.
As for your last question about how fast fruit flies should evolve, there is a long running study of the Galapagos finches (described in "The Beak of the Finch", by Jonathan Weiner), which has found that the finch populations actually change quite quickly in response to changes in the environment. But, the thing that keeps them from rapidly evolving into something completely different is that, most of the time, the conditions aren't changing. So, if they are well-adapted to the existing conditions, and the conditions aren't changing, the birds don't change either. Differences from the norm are less well-adapted, and so aren't as succesful as the rest of the population. It is only when conditions shift so that the bulk of the population is no longer so well-adapted that the variants start doing better.
And I think this would apply equally well to the fruit flies. Fruit flies are very well suited for what they do, and they have plenty of environments where they can do it. So, in a constant environment, why should they change? Particularly in a laboratory, where they are raised in pretty close to ideal conditions for fruit flies. There will be random variations around an optimum, but no particular pressure to become something different. But, if something new comes into the environment, like a new food plant, then a part of their population can quickly split off to start eating it (which is the basic topic of that first paper I listed above).
And not really related, other than being about weird animals:
A six-year-old boy draws pictures, and then his dad uses Photoshop to make them "real"
Tim Eisele: "KT: regarding the chromosome numbers, I agree that it is not entirely clear how the changes in chromosome numbers happen."
Now there is an understatement.
Tim Eisele: "It raises obvious who-do-I-mate-with-now? issues, and it is clearly fantastically rare, otherwise we'd see it happening before our eyes all the time."
And no way to answer the question, absent both high intelligence and knowledge.
Actually, changes in chromosome number happen all the time. For example, according to the last figures I recall reading (some years ago), about 1 in 900 human births involve a change in chromosome number. I'm not talking about someting like Down Syndrome. These are changes that don't cause such obvious reproductive dead-ends as Down; yet, they *are* reproductive dead-ends. For, to better state your note (*), else we'd see children and grandchildren born to the persons so affected, all the time.
But, there are no "chromosomal races" (as they are called) amongst humans. By way of contrast, there are known "chromosomal races" amonst the house mice.
Tim Eisele: "But I'd also like to note that while a change in chromosome number would be sufficient to make a new species ..."
Is it sufficient? What does "species" even mean?
How can a sexually reproducing "species" containing only one menber (**) reproduce, and thus survive?
(*) Notice, that statement by Me Eisle *was* a note, and not merely an assertion
(**) Actually, in most such cases, the first member of the "species" would be more in the nature of a hybrid between the "old" or "parent" species and the not-yet-existing "new" or "daughter" species. And assuming "species" even means anything.
Thank you for the search term, Ilion. "Chromosomal races" lets me sift through the papers on fruit flies to find the sort of thing that KT was asking about. Here's one that looks promising (I'm linking to this one in particular because it is the first one in the search list that is downloadable without paying a fee):
Chromosomal basis of raciation in Drosophila: A study with Drosophila nasuta and Drosophila albomicana.
The abstract says that they were using two strains of fruit flies, which have the interesting trait that one has 6 chromosomes, while the other has 8. But, in spite of this, they are not only able to breed with each other, their offspring are also fertile, and in fact they've bred the crosses into new, distinct, genetically stable strains.
The key point I get from this is that when I was assuming that a change in chromosome number was necessarily a barrier to breeding with the parent stock, I was mistaken. This work pretty clearly shows that chromosome number is just a trait, like other traits, and these traits can change when conditions are right while still allowing the ones that changed to successfully mate and have offspring.
So basically, the conflation of chromosome number changes with species looks to be something of a red herring.
Tim Eisele: "The key point I get from this is that when I was assuming that a change in chromosome number was necessarily a barrier to breeding with the parent stock, I was mistaken. This work pretty clearly shows that chromosome number is just a trait, like other traits, and these traits can change when conditions are right while still allowing the ones that changed to successfully mate and have offspring."
Now you're making the opposite mistake. Chromosome number is *not* "just a trait, like other traits". A difference in chromosome number does not necessarily interfere with interbreeding between two stocks, though it frequently/generally does. There are many variables, amongst which are (non-exhaustively) --
- the type of organisms: fruitflies, elephants, and cabbages are wildly different organisms, and chromosomal abnormalities affect them differently;
- the type of the difference in chromosome number, that is, how the difference came to be;
- at least with mammals, the specific sex of the organism having the novel chromosome difference;
Tim Eisele: "So basically, the conflation of chromosome number changes with species looks to be something of a red herring."
Not at all. It's just, as the saying goes, complicated.
And, as I've said before, it is the focus on speciation that is the red-herring ... even aside form the fact that 'species' has not real definition.
Forcing a population of fruitflies to be reproductively isolated from other populations of fruitflies does not even begin to explain fruitflies.
Selectively eliminating whole suites of gene alleles from different sub-populations of wolves, to the point that the sub-populations are barely recognizable as being of the same species, does not even begin to explain wolves.
me: "A difference in chromosome number does not necessarily interfere with interbreeding between two stocks, though it frequently/generally does. There are many variables, amongst which are (non-exhaustively) --
- the type of organisms: fruitflies, elephants, and cabbages are wildly different organisms, and chromosomal abnormalities affect them differently;
- the type of the difference in chromosome number, that is, how the difference came to be;
- at least with mammals, the specific sex of the organism having the novel chromosome difference;"
Above, by the phrase "with interbreeding between two stocks", I had in mind not something like the crossing of horses and asses (which two species do, indeed, have different numbers of chromosomes ... and yet, which produce viable, if generally infertile, offspring), nor something like the crossing of lions and tigers (which species have the same numbers of chromosomes, and which produce viable, if generally infertile, offspring), but rather the crossing of individuals of two different sub-populations of the *same* species, which, however it came to be, have different numbers of chromosomes, such as the "chromosomal races" of the house mouse.
Now, in a case like this, there may or may not be a problem in the initial crossing. That is, depending on how different the total genome of the species has been "repackaged" (so to speak) between the two "chromosomal races", the embryos resulting from such crosses may be non-viable. This is because when the egg and sperm of the different "races" unite, the resulting zygote may be missing critical genes, or may have extra copies of some genes.
But, even if the embryos produced by the cross are viable, their fertility is still affected. It's just that they are not necessarily completely infertile. They will, however, always be less fertile than the parent stocks, just not necessarily completely infertile.
Also -- amongst mammals -- this reduced fertility affects the males even more than the females. Amongst birds, it would be the opposite (this is because the chromosomal sex-determination system of mammals and birds are "opposite" so to speak). The particular "law" I'm referencing here is known as "Haldane's Law".
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